I have never really built anything too complicated from scratch, only followed pre-made guides and I'm looking for some help. Basically I bought a 12V 15RPM motor that I will have hooked up to a remote activated outlet plug. I want to make a circuit that will, when the power is activated from the plug, turn the motor on for somewhere between 1-5 seconds (I haven't decided yet) and then turn it off. Can someone help me figure out a method for doing this? Your help is much appreciated. Thanks

So I'm assuming if I drop the voltage to 12v the current is doubled to .6 amps, correct? Now what can I use at the end to bring the voltage back up to 24v? And I'm having trouble finding a 100k resistor like the one in the diagram that is suitable for 24v .3 amps (~8watts), anyone have any ideas? Thanks for the help guys

OK, how much current does the 12V motor draw maximum, in the start/stalled condition? How much current does each of the solenoid valves draw? Are there any other things attached to this we will need to take into account.

I'm waiting on the specs for the 12v motor, but I'm not as concerned about that. The solenoids will be operating on 24v 0.3Amps. There won't be anything else attached to the circuit. I just simply need them to open for a short amount of time, and then shut, and the circuit to not retrigger them to open. And then power will be cut from the circuit after a short amount of time

Wow! Thanks so much for the diagram, much appreciated! I just have a few questions if you don't mind. For the 24v circuit, you used a 1N4742A zener diode, but it says its only rated for 1W, isn't that too small? Doesn't everything have to be rated for like ~8W? And Which of the capacitors/resistors do I have to adjust to adjust to output time? Could you recommend a good site to order all or most of this stuff? Instead of hunting around for each part. Thanks again for all your help!

The zener only supplies current to the timer circuit that draws very little, so 1W should be sufficient. R3 is a potentiometer used as a variable resistor to adjust the time. I'll take a look at the components and give you a vendor.

Ken,
Shouldn't use a Zener like that. You need the circuit voltage regulated, not the drop from 24v down to the timer voltage. You take a chance that a spike will zap the circuit; and you're using a CMOS timer and a MOSFET for a driver. Odds are that one spike will kill them both.

...So, what would you suggest? And since the zener is only rated for 1W does that mean I can use capacitors and resistors for 1W as well? I was under the impression I needed something that parts that could support about 8W for everything. Thanks again for all the help guys